1. Field of the Invention
The present invention relates to a turret punch press, and, in particular, to a mechanical turret punch press in which an upper tool is actuated jointly by both a mechanical striker and a hydraulic striker.
2. Description of the Prior Art
Conventionally, a commonly known turret punch press comprises a freely rotatable upper turret equipped with a plurality of freely detachable upper tools, a freely rotatable lower turret in opposition to the upper turret, and a freely vertically mobile striker which strikes the upper tool in the processing position. A disk support which supports the lower turret is provided on the lower side of the lower turret in the processing position for resisting the impact from a striking element.
During a forming process, the upper turret and the lower turret are rotated in sychronism and a pair of dies for specific forming is positioned in the processing position, a workpiece is positioned between the two dies, and the forming process is performed by pressing the upper and lower dies together using a mechanical or a hydraulic device.
However, in the above-mentioned mechanical type of punch press, because the forming die is not formed with a through hole, a forming punch (the upper die) which is suddenly dropped, impacts a forming die (the lower die) and an excess force acts on the die, or a die holder, or on the lower turret, or the like, so that there is concern about damage or breakage. For this reason, a difficult height adjustment must be scrupulously performed from time to time to change the height of the die.
In the case of a punch press using a hydraulic device, it is possible to prevent any excess force from acting on the die or the die holder, or on the lower turret, or the like, but frequent use of the hydraulic device shortens the life span of a large number of parts. In addition, the hydraulic device is expensive which is a disadvantage from the aspect of operating costs.